MGL FF-1 fuel gauge & problem with RV-4 fuel senders

[jamlip]

I am trying to calibrate an MGL FF-1 digital fuel gauge that I have fitted in my RV-4.



Unfortunately, on trying to calibrate the MGL gauge, the output voltage from the senders is bouncing-around all over the place. I understand that float senders are not very accurate in an aircraft wing tank, but even when the aircraft is stationary, with no fuel sloshing-around, the voltage output fluctuates wildly.

I have checked the ground on the FF-1 and from the tank to the panel ground bus and it's all good.

The aircraft is 30 years old and I didn't build it, so I'm unsure what fuel senders are fitted. Prior to fitting the MGL FF-1, fuel level was displayed on two of these SW automotive-style gauges, which seemed reasonably(ish) accurate:



I'm wondering, what is the likelihood of this being a sender issue? Would fitting new senders in my tanks solve the problem?

If so, does anyone have instructions on how to get at them?

Is it possible to retrofit capacitance senders in my tanks for more accurate fuel level readings?

Any help much appreciated!